A natural joint may undergo degenerative changes due to a variety of etiologies. When these degenerative changes become so far advanced and irreversible, it may ultimately become desirable or necessary to replace the natural joint with a prosthetic joint. When implantation of such a joint prosthesis is implemented, the head of the natural bone, such as a femur, tibia or humerus, can be first resected and then a canal can be created within the medullary cavity of the host bone for accepting and supporting the prosthetic joint.
Because different patients have bones of various shapes, it is necessary to have available different appropriately structured prosthetic joint implants to accommodate these different shapes. Moreover, different patients having host bones with substantially the same sized medullary cavities may have differently shaped bone heads and necks, or vice versa. Consequently, a prosthetic joint assembly that has a diaphyseal portion that is appropriate for one host bone medullary cavity may not have an epiphyseal portion that is appropriate for the neck of the host bone. Thus, the most desirable fit may not always be possible, which can result in adverse effects on joint motion and patient comfort. Accordingly, it has become practice in the art to have prosthetic joint implants of different sizes, as described in U.S. Pat. No. 5,342,366 to Whiteside et al.
In order to determine which prosthetic joint implant to use with each patient, intraoperative procedures are sometimes used to measure various geometries of the host bone. It is particularly desirable to know the diameter of the stem at the diaphyseal portion of the prosthetic joint implant that will be implanted in the host bone and thus, the width to which to make the intramedullary canal. In preparing the medullary cavity for receiving the stem, it is desirable to remove some of the cancellous bone and/or make an implant shaped cavity within the cancellous bone from within the cortical bone in order to support the implant. As such, the implant will engage the cortical bone to facilitate osseointegration with the cortical bone wall. Additionally, it is desirable to not damage the cortical bone wall while reaming the bone canal because the cortical bone wall provides a substantial portion of the strength and rigidity of the host bone. Typically, doctors must remove the cancellous bone manually with a reamer, and a broach, as is described in U.S. Patent Application Pub. No. 2014/0128987 to Kelley and U.S. Pat. No. 6,517,581 to Blamey.